Electric switch with permanentmagnet blowout field



Sept. 16, 1952 R. B. IMMEL ETAL 2,611,059

ELECTRIC SWITCH WITH PERMANENT-MAGNET BLOWOUT FIELD Filed July 7, 1950Fig.1. Fig.2.

I 8 I 3 B I 3 l '0"? o l8 L 25 |8 "W 6 25 L a? "11, 5 7 4 5 '9 v 7 k u i9 I I2 22 H 4 l4 u I 6 l4 L- :22- a I- 2. l5 g l5 vi/masses: INVENTORSRalph B. Immel and I Lawrence Pierce. 77%;? flu! '--/*-1 ATTORNEYPatented Sept. 16, 1952 ELECTRIC SWITCH WITH PERMANENT- MAGNET BLOWOUTFIELD Ralph E. Immel, Wiliiamsviile, and Lawrence Pierce, Buffalo, N.Y., assignors to Westinghouse Electric Corporation, East Pittsburgh,Pa., a corporation of Pennsylvania Application July 7, 1950, Serial No.172,522

3 Claims. 1

Our invention relates to manually or automatically operated electricswitches and more particularly to switch contact devices with1plermanent magnets to provide an arc blowout eld.

Known devices of this kind have, for each interrupting gap, a singlepermanent magnet mounted staticnarily in the vicinity of the stationaryswitch contacts. Unless the magnet is very large and thus occupiesconsiderable space in excess of that needed by the contact deviceproper, the blowout eflect and, accordingly, the interrupting rating ofthese known devices are rather limited.

It is an object of our invention to materially increase the interruptingrating of switching devices of the above-mentioned kind by providing ablowout field of higher intensity or eiiectiveness with the aid ofpermanent magnets of simple design and little or no space requirementsin excess of the space needed for the switching devices proper. Another,related ob- .iect of the invention is to provide a permanentmagnetblowout unit that is generally suitable for direct-current contactdevices and can readily be substituted for devices without blowout bymounting it in the same place and space.

To achieve these objects, and in accordance with the invention, we mounta permanent magnet behind the stationary contact member of the switchingdevice and mount another permanent magnet on and behind the appertainingmovable contact member in sufiiciently close magnetic relation to thestationary magnet to jointly produce a blowout field not only of higherintensity but also of a more favorable orientation than otherwiseobtainable, these and other features of the invention being apparentfrom the embodiment exemplified on the drawing and described in thefollowing:

In the drawing, Fig. 1 is a part-sectional side view of a switchingdevice according to the invention in closed condition; Fig. 2 is asimilar view but shows the device in open condition; Fig. 3 is aperspective view of the same device during opening performance; and Fig.4 is an explanatory illustration showing a section through the contactmembers and permanent magnets in a relative position corresponding toFig. 3 and schematically representing the blowout field by lines offorce.

The drawing demonstrates the invention in its application to a manuallyoperated cam-type master or control switch although it should beunderstood that the invention is applicable to all types of switchingdevices involving a mom ing contact and a stationary contact in whichthe are drawn between the contacts, during separation of the movablecontact from the stationary contact, is to be extinguished by means of apermanent magnetfield.

The illustrated switching device has an insulating panel or base I. Astationary contact memher 2 is mounted on the base I by a threaded stud3 which serves also as an electrical terminal. Another stationarycontact member 4 is positioned beneath assembly 2 and secured to base Iby a stud 5 which serves also as an electrical terminal.

The contact members 2 and 4 carry respective contact buttons 6 and lwhich areengageable with respective contact buttons 8 and S of a movablecontact bridge iii. The contact buttons consist preferably of goodelectrical conducting material, for example, silver. The bridge i8 isresiliently secured to an arm [I which is pivoted at 2 in a support i3.Support :3 is firmly attached to base I by a screw it and is indexed bymeans of a dowel pin 15 engaging a hole in the base I. The resilientmounting for bridge I0 includesa pin I! which is fitted through a holein arm H and passes through a clearance hole ofv bridge It. Bridge It!can slide along pin 1'! and is biased toward a supporting surface of armII by a compression spring I8. Spring i8 is seated on pin l1, betweenthe bridge to and a washer 19 at the extremity of pin H.

The movable arm II is biased in a clockwise direction, as viewed in Fig.1, by a compression spring 20, which isdisposed between a shoulder 2| onthe movable arm I! and seats against the bottom of a hole 22 in thesupporting member l3. Spring 29 tends to force the movable contactassembly against the stationary contact assemblies under compression ofthe weaker spring 53.

In this application, the movable arm H is cam actuated and to this endis provided with a roller 23 which is pivotally mounted at a pointdisplaced from the pivot I2. Roller 23 is engageable by a control cam25. Rotation of the cam from the position shown in Fig. 1 to a positionin which it engages the roller 23 results in counterclockwise rotationof the movable member to the switch-opening position shown in Fig. 2.

The stationary contact member 2 is U-shaped. A permanent magnet 25 issecured between the U-legs of the member. Magnet 25 is also U-shaped andhas its north and south pole ends, marked N and S in Fig. 4, abutagainst the one leg of member 2 that carries the contact button 6. Themovable bridge member II] has a U-shaped end portion near contact buttonit. Another permanent magnet 26 is secured between the legs of this endportion. Magnet 26 is also U-shaped and has its pole ends, marked N andS in Fig. 4, in abutment with the one leg of bridge that carries theadjacent contact button 8.

The two magnets and 26 consist of a material of high coercive force andhigh remanence, for instance, of a sintered .aluminumeni'ckel cobaltalloy, although other permanentmagn'ets of highly magnetic material arealso suitable. The material of the stationary contact member 2 and thebridge I 0 is nonmagnetic, andallother parts of the stationary andmovable contact assemblies are preferably also nonmagnetic.

Magnet 26 is held in place by a set screw shown at 21 in Figs. 1 and 3.The set screw engages a small dowel hole of the magnet. Magnet 25 issimilarly fastened to'member 2 by a chamfer of screw 3 which entersintoa small dowel recess'of' the magnet. Other ways of fastening themagnets, of course, may be used, but the one just mentioned is simpleand prevents damaging the magnets mechanically or magneticallyespecially if magnets as brittle as aluminum nickelcobalt type magnetsare used.

The arrangement or poling of the two permanent magnets is'such thatrespective poles' of like polarity lie at thesame side 'of the switchingdevice as is apparent from'Fig'. 4. .Polin'g the magnets in this mannerconcentrates thefield at the place where the contacts separate andresults in lines of force approximately parallel' to the contactsurfaces and perpendicular to'the arc. The. relationship of current flowin the'arc, magnetic field direction, and are movement then obtaining iselucidated byarrowsin Fig. Sand Fig. 4. In Fig. 3 the'arrows Cindicatethe.direction of current flow undergivenconditions, and the'arrow markedCurrentfin the top portion and below the illustration of structure .inFig. 3 denotes the'corr'esponding direction of .current flow in thearc.Arrows Fs in Figs- 3 and 4 denote the prevailing force line directions.of the stationary magneticfield component while arrows Fm in bothfigures denote the corresponding prevailing directions for'the movablemagnet field. The resultant field direction is denoted by the arrowmarked Field at the bottom of Fig. 3 for the indicated north (N) andsouth (S polarity arrangement of the magnets. The direction of the arcmovement is denoted in Fig. 3 by the arrows marked Arc.

As thus made apparent in Figs. 3 and'4, the resultant magnetic flux isconcentrated in one desirable path perpendicularto the arc. It may bementioned that this condition and theresulting improvement in arcextinction and interrupting capacity. is obtained .only .if oppositepoles of the respective magnetsareof like polarity. If .these polesare.of the opposite polarity, the flux is concentrated not inonedesirablepath, but. in. two. less desirable paths parallel to .the arc,and the .result, .as tests have shown, is no betterthan when onemagnetonly is mounted on the stationary. contact assembly.

Devices accordingto theinventionare especially advantageous for switchesthatmayinvolve a slow-operating contact separation. .For instance asidefrom. manual switches. theinvention is particularly well suitedas a.limit switch for motor operatedrheostats. .Insuch'applications, therheostat mechanism may open the contact very slowly so that the contactsurfaces of the customary switches may become damaged by burning beforethe arc is extinguished, while such defects are greatly minimized orprevented by the invention. However, fast-operating switching devices aswell as switching apparatus other than. hereinspeciflcally mentionedal'so-benefitfrom-the invention in permitting a higher interruptingrating; and it will also be obvious to those skilled in the art thatchanges and modifications in design, arrangement and structuralldetails,can readily be made without d'eparturelfrom the objects and essentialfeatures .of the invention.

We claim as our. invention:

1. I'm anelectric. switching device, the combinationincluding, a base ofinsulating material, a contact member stationarily mounted on the base,"a stationary permanent magnet mounted substantially behind thestationary contact member and having respective north and south polesdirected away from the base, a movable contact member having a U-shapedportion with two parallel legs. andibeing, engageable at the outside of.one of said legs with said stationary contact member, a movablepermanent magnet mounted onthe. U-shaped. portion between. the. two legsof the .U and. having respective. north and south poles directed. towardthe stationary permanent magnet, said twomagnetshaving respective polesotlike polarities. substantially facing each other.

2-. .In an-electric switching device, the combination including, abase.of insulating material, a stationary U-shaped member mounted on the basewith one leg against the base and theother leg disposed away from thebase, a stationary contact fixed to the .outer surface of the said otherleg, a one piece permanent magnet mounted inthe'bight' of the U andhaving its poles disposed substantially at the respective sides of thestationary contact, amovable U-shaped member disposed substantiallyopposite the stationary U-shaped member, a movable contact fixed to theouter surface of the legof the movable U-shaped memberin relation forengagement with the stationarycontact, a one piece permanent magnetmounted inthebight of the U of the movable U-shaped member and havingits poles disposed substantially at the respective sides of the movable:contact, said two magnets having respective poles of like; polaritiessubstantially facing each other.

:3.:In-an-electricswitching device, the combinationincluding, a base ofinsulating material, a Ueshaped member mounted on the base with one legof the U against the base and the other facing outwardly, or away, fromthe base, an upper stationary contact mounted on the outer surface'efthe outer leg of the U, a lower stationary contact mounted'on the basesubstantially in the plane of the upper stationary contact,-an armpivoted below the lower stationary ccntact abontact bridging member,having an upper contact and a lower-contact, for bridgingthe'stationary'contacts, said contact bridging member.being-mountedonthe-arm whereby the upper contacts'are disposed a greater distancefrom'each'otherwhen" the arm moves the contact bridging member, awayfrom the stationary contacts,..a one piece U-shaped permanent mag- .netmounted in the U-shaped member so that the poles thereof aresubstantially at the sides of the up er. stationary contact, a one pieceU-shaped permanent ma net similarly mounted with respect tofthe uppermovable contacts, said two magnetshaying respective poles of likepolarities disposed to substantially face each other.

The following references are of record in the file of this patent:

6 UNITED STATES PATENTS Number Name Date E Q IMMEL- E 2,180,147 HoppNov. 14, 1939 WRENCE PIERC 5 2,237,278 Willing Apr. 1, 1941 2,340,682Powell Feb. 1, 1944 REFERENCES CITED 2,356,039 Ellis et a1 Aug. 15, 1944

